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THIS region occupies a sandy stratum known as the Woodbine Sand, which lies at the base of the Upper Cretaceous group of rock beds and outcrops substantially as indicated on the map (Plate 1). The woody dominants are essentially the same in regions 14 and 15, with the Eastern Cross Timbers having the advantage of several more inches of average rainfall per year. This tends to produce somewhat larger timber here, on the average, than is found in the Western Cross Timbers. A timbered strip of sandy soil bordering Red River-except for a short gap in northern Cooke County where the prairie touches the river-connects regions 14 and 15 with each other and with region 16. Practically the same grasses and showy wild-flowers are common to both these timbered strips and also to region 16.